Here's why:
* Direct Object: The direct object receives the action of the verb. In this case, the verb is "was" (a form of the verb "to be"), and the action is being the star.
* Indirect Object: An indirect object receives the direct object. There isn't one in this sentence.
* Predicate Adjective: A predicate adjective modifies the subject and follows a linking verb. "Star" is a noun, not an adjective.
* Nominative: A nominative is a noun that acts as the subject of the sentence. "Pamela" is the subject, not the nominative.
To make it clearer:
The sentence means "Pamela was the star of the play." The phrase "the star of the play" is the direct object of the verb "was."